This invention relates generally to refrigeration and, more particularly, to the use of multiple component refrigerant fluids useful for generating refrigeration. The invention is particularly useful for providing refrigeration down to cryogenic temperatures.
Refrigeration is conventionally generated by compressing and then expanding a refrigerant fluid within a refrigeration circuit. Well known examples of such conventional systems include refrigerators and air conditioners. Typically the refrigerant is a single component fluid which undergoes a phase change at a required temperature from a liquid to a gas thus making its latent heat of vaporization available for cooling purposes. The efficiency of the conventional system can be improved by using a multiple component fluid as the refrigerant which can provide variable amounts of refrigeration over a required temperature range. However, known multiple component fluid refrigeration cycles cannot effectively provide refrigeration over a large temperature range down to colder cryogenic temperatures. Moreover, most well known refrigerant fluids are toxic, flammable and/or ozone depleting.
Accordingly it is an object of this invention to provide a method for generating refrigeration using a multiple component refrigerant fluid which can provide refrigeration over a large temperature range down to cryogenic temperatures.
It is another object of this invention to provide a multiple component refrigerant fluid which is non-toxic, non-flammable, and low or non-ozone-depleting.
The above and other objects, which will become apparent to those skilled in the art upon a reading of this disclosure, are attained by the present invention, one aspect of which is:
A method for generating refrigeration comprising:
(A) compressing a variable load refrigerant mixture comprising at least one component from the group consisting of fluorocarbons, hydrofluorocarbons and fluoroethers and at least one component from the group consisting of fluorocarbons, hydrofluorocarbons, hydrochlorofluorocarbons, fluoroethers, atmospheric gases and hydrocarbons to produce a compressed variable load refrigerant mixture;
(B) cooling the compressed variable load refrigerant mixture to produce a cooled compressed variable load refrigerant mixture;
(C) expanding the cooled, compressed variable load refrigerant mixture and generating refrigeration to produce a lower temperature variable load refrigerant mixture; and
(D) warming the lower temperature variable load refrigerant mixture.
Another aspect of the invention is:
A refrigerant mixture which is non-toxic, non-flammable and low-ozone-depleting comprising at least one component from the group consisting of fluorocarbons, hydrofluorocarbons and fluoroethers and at least one component from the group consisting of fluorocarbons, hydrofluorocarbons, hydrochlorofluorocarbons, fluoroethers, atmospheric gases and hydrocarbons.
As used herein the term xe2x80x9cvariable load refrigerantxe2x80x9d means a mixture of two or more components in proportions such that the liquid phase of those components undergoes a continuous and increasing temperature change between the bubble point and the dew point of the mixture. The bubble point of the mixture is the temperature, at a given pressure, wherein the mixture is all in the liquid phase but addition of heat will initiate formation of a vapor phase in equilibrium with the liquid phase. The dew point of the mixture is the temperature, at a given pressure, wherein the mixture is all in the vapor phase but extraction of heat will initiate formation of a liquid phase in equilibrium with the vapor phase. Hence, the temperature region between the bubble point and the dew point of the mixture is the region wherein both liquid and vapor phases coexist in equilibrium. In the practice of this invention the temperature differences between the bubble point and the dew point for the variable load refrigerant is at least 10xc2x0 K, preferably at least 20xc2x0 K and most preferably at least 50xc2x0 K.
As used herein the term xe2x80x9cfluorocarbonxe2x80x9d means one of the following: tetrafluoromethane (CF4), perfluoroethane (C2F6), perfluoropropane (C3F8), perfluorobutane (C4F10), perfluoropentane (C5F12), perfluoroethene (C2F4), perfluoropropene (C3F6), perfluorobutene (C4F8), perfluoropentene (C5F10), hexafluorocyclopropane (cyclo-C3F6) and octafluorocyclobutane (cyclo-C4F8).
As used herein the term xe2x80x9chydrofluorocarbonxe2x80x9d means one of the following: fluoroform (CHF3), pentafluoroethane (C2HF5), tetrafluoroethane (C2H2F4), heptafluoropropane (C3HF7), hexafluoropropane (C3H2F6), pentafluoropropane (C3H3F5), tetrafluoropropane (C3H4F4), nonafluorobutane (C4HF9), octafluorobutane (C4H2F8), undecafluoropentane (C5HF11), methyl fluoride (CH3F), difluoromethane (CH2F2), ethyl fluoride (C2H5F), difluoroethane (C2H4F2), trifluoroethane (C2H3F3), difluoroethene (C2H2F2), trifluoroethene (C2HF3), fluoroethene (C2H3F), pentafluoropropene (C3HF5), tetrafluoropropene (C3H2F4), trifluoropropene (C3H3F3), difluoropropene (C3H4F2), heptafluorobutene (C4HF7), hexafluorobutene (C4H2F6) and nonafluoropentene (C5HF9).
As used herein the term xe2x80x9chydrochlorofluorocarbonxe2x80x9d means one of the following: chlorodifluoromethane (CHClF2), chlorofluoromethane (CH2ClF), chloromethane (CH3Cl), dichlorofluoromethane (CHCl2F), chlorotetrafluoroethane (C2HClF4), chlorotrifluoroethane (C2H2ClF3), chlorodifluoroethane (C2H3ClF2), chlorofluoroethane (C2H4ClF), chloroethane (C2H5Cl), dichlorotrifluoroethane (C2HCl2F3), dichlorodifluoroethane (C2H2Cl2F2), dichlorofluoroethane (C2H3Cl2F), dichloroethane (C2H4Cl2), trichlorofluoroethane (C2H2Cl3F), trichlorodifluoroethane (C2HCl3F2), trichloroethane (C2H3Cl3), tetrachlorofluoroethane (C2HCl4F), chloroethene (C2H3Cl), dichloroethene (C2H2Cl2), dichlorofluoroethene (C2H2ClF) and dichlorodifluoroethene (C2HClF2).
As used herein the term xe2x80x9cfluoroetherxe2x80x9d means one of the following: trifluoromethyoxy-perfluoromethane (CF3xe2x80x94Oxe2x80x94CF3), difluoromethoxy-perfluoromethane (CHF2xe2x80x94Oxe2x80x94CF3), fluoromethoxy-perfluoromethane (CH2Fxe2x80x94Oxe2x80x94CF3), difluoromethoxy-difluoromethane (CHF2xe2x80x94Oxe2x80x94CHF2), difluoromethoxy-perfluoroethane (CHF2xe2x80x94Oxe2x80x94C2F5), difluoromethoxy-1,2,2,2-tetrafluoroethane (CHF2xe2x80x94Oxe2x80x94C2HF4), difluoromethoxy-1,1,2,2-tetrafluoroethane (CHF2xe2x80x94Oxe2x80x94C2HF4), perfluoroethoxyfluoromethane (C2F5xe2x80x94Oxe2x80x94CH2F), perfluoromethoxy-1,1,2-trifluoroethane (CF3xe2x80x94Oxe2x80x94C2H2F3), perfluoromethoxy-1,2,2-trifluoroethane (CF3Oxe2x80x94C2H2F3), cyclo-1,1,2,2-tetrafluoropropylether (Cyclo-C3H2F4xe2x80x94Oxe2x80x94), cyclo-1,1,3,3-tetrafluoropropylether (cyclo-C3H2F4xe2x80x94Oxe2x80x94), perfluoromethoxy-1,1,2,2-tetrafluoroethane (CF3xe2x80x94Oxe2x80x94C2HF4), cyclo-1,1,2,3,3-pentafluoropropylether (cyclo-C3H5xe2x80x94Oxe2x80x94), perfluoromethoxy-perfluoroacetone (CF3xe2x80x94Oxe2x80x94CF2xe2x80x94Oxe2x80x94CF3), perfluoromethoxy-perfluoroethane (CF3xe2x80x94Oxe2x80x94C2F5), perfluoromethoxy-1,2,2,2-tetrafluoroethane (CF3xe2x80x94Oxe2x80x94C2HF4), perfluoromethoxy-2,2,2-trifluoroethane (CF3xe2x80x94Oxe2x80x94C2H2F3), cyclo-perfluoromethoxy-perfluoroacetone (cyclo-CF2xe2x80x94Oxe2x80x94CF2xe2x80x94Oxe2x80x94CF2xe2x80x94) and cyclo-perfluoropropylether (cyclo-C3F6xe2x80x94O).
As used herein the term xe2x80x9catmospheric gasxe2x80x9d means one of the following: nitrogen (N2), argon (Ar), krypton (Kr), xenon (Xe), neon (Ne), carbon dioxide (CO2), oxygen (O2) and helium (He).
As used herein the term xe2x80x9chydrocarbonxe2x80x9d means one of the following: hydrogen (H2), methane (CH4), ethane (C2H6), ethene (C2H4), propane (C3H8), propene (C3H6), butane (C4H10), butene (C4H8), cyclopropane (C3H6) and cyclobutane (C4H8).
As used herein the term xe2x80x9cnon-toxicxe2x80x9d means not posing an acute or chronic hazard when handled in accordance with acceptable exposure limits.
As used herein the term xe2x80x9cnon-flammablexe2x80x9d means either having no flash point or a very high flash point of at least 600xc2x0 K.
As used herein the term xe2x80x9clow-ozone-depletingxe2x80x9d means having an ozone depleting potential less than 0.15 as defined by the Montreal Protocol convention wherein dichlorofluoromethane (CCl2F2) has an ozone depleting potential of 1.0.
As used herein the term xe2x80x9cnon-ozone-depletingxe2x80x9d means having no component which contains a chlorine, bromine or iodine atom.
As used herein the term xe2x80x9cnormal boiling pointxe2x80x9d means the boiling temperature at 1 standard atmosphere pressure, i.e. 14.696 pounds per square inch absolute.
As used herein the term xe2x80x9ccryogenic temperaturexe2x80x9d means a temperature of 150xc2x0 K or less.
As used herein the term xe2x80x9cindirect heat exchangexe2x80x9d means the bringing of two fluids into heat exchange relation without any physical contact or intermixing of the fluids with each other.
As used herein the term xe2x80x9cexpansionxe2x80x9d means to effect a reduction in pressure.
As used herein the terms xe2x80x9cturboexpansionxe2x80x9d and xe2x80x9cturboexpanderxe2x80x9d mean respectively method and apparatus for the flow of high pressure fluid through a turbine to reduce the pressure and the temperature of the fluid thereby generating refrigeration.